A search log of search queries may be useful for determining query patterns common among search queries. The query patterns may be useful for various purposes, such as generating and/or ranking alternative query suggestions, ranking search results, and so forth. However, some search queries may include private user information. This is particularly true in contexts in which the search queries are submitted to systems that are deemed private to the user and/or to an entity with which the user is associated (e.g., her employer). For example, many personal or intra-entity systems such as email systems, filesystems, document management systems, etc., may be searched by users using search queries that are relatively likely to contain private information, such as names, contact information, account numbers, and so forth.